In the conventional high frequency apparatus relating to the above described tuner for PSK or PAM data applications, the inductance of the tuning portion of a voltage controlled oscillator may be formed with a strip type transmission line to withstand vibration.
Namely, if the inductance is formed with a coil, for example, a vibration may cause vibration of the wire of the coil, which induces a shift in the inductance value, resulting in displacement of tuned frequency. In order to avoid the occurrence of such phenomenon, the inductance may be formed with a strip type transmission line of copper foil fixed on a substrate for securing stability against vibration.
A problem in the above described structure, where the inductance of the tuning portion is comprised of a strip type transmission line alone, is that fine tuning adjustment is not easy. This is because variations due to constants and mounting positions of electronic components constituting the local oscillator are compensated for before completion.